全文获取类型
收费全文 | 1429篇 |
免费 | 20篇 |
国内免费 | 18篇 |
专业分类
化学 | 987篇 |
晶体学 | 25篇 |
力学 | 24篇 |
数学 | 245篇 |
物理学 | 186篇 |
出版年
2023年 | 8篇 |
2022年 | 8篇 |
2021年 | 10篇 |
2020年 | 18篇 |
2019年 | 8篇 |
2018年 | 6篇 |
2017年 | 8篇 |
2016年 | 22篇 |
2015年 | 18篇 |
2014年 | 20篇 |
2013年 | 66篇 |
2012年 | 62篇 |
2011年 | 86篇 |
2010年 | 45篇 |
2009年 | 51篇 |
2008年 | 101篇 |
2007年 | 104篇 |
2006年 | 88篇 |
2005年 | 67篇 |
2004年 | 70篇 |
2003年 | 77篇 |
2002年 | 81篇 |
2001年 | 24篇 |
2000年 | 30篇 |
1999年 | 23篇 |
1998年 | 21篇 |
1997年 | 18篇 |
1996年 | 34篇 |
1995年 | 11篇 |
1994年 | 17篇 |
1993年 | 11篇 |
1992年 | 19篇 |
1991年 | 9篇 |
1989年 | 12篇 |
1987年 | 6篇 |
1986年 | 11篇 |
1985年 | 17篇 |
1984年 | 13篇 |
1983年 | 7篇 |
1982年 | 17篇 |
1981年 | 25篇 |
1980年 | 13篇 |
1979年 | 19篇 |
1978年 | 18篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 10篇 |
1974年 | 7篇 |
1973年 | 5篇 |
1972年 | 5篇 |
排序方式: 共有1467条查询结果,搜索用时 15 毫秒
991.
992.
Louis Cottier Gerard Descotes Romuald Skowronski Jaroslaw Lewkowski 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4)
Abstract Synthetical aspects of furylaminophosphonic acids are discussed here. 相似文献
993.
Erwan Galardon Michael Lukas Paul Le Maux Loïc Toupet Thierry Roisnel Gerard Simonneaux 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(8):955-956
The geometry about the Ru atom in the title compound, [Ru(C9H9N)2(C92H108N4O24)], is approximately tetragonal and the porphyrin ring is nearly planar, while the C—N—R angles [169.3 (3) and 163.9 (3)°] of the isocyanide ligands in the complex are different from the value of 180° expected in the free ligand. 相似文献
994.
Michel D. Meijer Arjan W. Kleij Martin Lutz Anthony L. Spek Gerard van Koten 《Journal of organometallic chemistry》2001,640(1-2):166-169
Treatment of the diaminobenzene [C6H4{CH2NMe2}2-1,3] (NCN-H, 1) with one or two equivalents of cis-PtCl2(DMSO)2 leads to exclusive formation of the doubly cycloplatinated species [C6H4{CH2NMe2}2-1,5-{PtCl(DMSO)}2-2,4] (3), which upon addition of triphenylphosphine yields the bisphosphine adduct [C6H4{CH2NMe2}2-1,5-{PtCl(PPh3)}2-2,4] (4). The X-ray molecular structure of 4 revealed the presence of highly distorted square planar Pt(II) centers which is caused by close proximity of the two phosphine donor ligands. Complexes of type 3 can be regarded as suitable starting materials for the directional build-up of larger macromolecular structures. 相似文献
995.
The influence of ball to powder ratio and discontinous milling during ball milling of Fe0.75C0.25 elemental powder mixture is presented. The formation of Fe3C cementite, Hägg and ε carbides has been follwed by X-ray diffraction and Mössbauer Spectroscopy. Higher ball to powder ratios induce faster kinetics. Synthesized cementite has crystallite sizes 9 to 11 nm. 相似文献
996.
997.
Multilayers of cobalt and niobium have been deposited in ultra high vacuum, using two E-beams onto both corning glass and silicon wafers substrates kept at 20°C. These films were then ion mixed using Xe ions at 200, 300 and 400 keV. The dose was 3 × 1015 ions cm-2 in all cases. FMR and usual magnetization measurements were made to characterize the samples. Films mixed at 300 and 400 keV are homogeneous. FMR line width of 60 Oe and the simple spectra obtained lead us to conclude that these films are much more homogeneous than co-evaporated amorphous films of the same composition. 相似文献
998.
Eckhoff's conjecture for the Τ-Radon numbers r(Τ) of a convexity space. (X,C) says r(Τ) ≦ (r?1)(Τ?1)+1, with r = r(2). The main result of this note is that Eckhoff's conjecture is true in case ¦X¦ ≦ 2r and Τ = 3, i.e. each (2r?1)-set in a space with 2r?1 or 2r elements has a 3-Radon partition. 相似文献
999.
1000.
Jeffrey S Albert David Aharony Bruce T Dembofsky Gerard M Koether William Potts John L Evenden 《Tetrahedron》2004,60(20):4337-4347
We have previously described a series of antagonists that showed high potency and selectivity for the NK1 receptor. However, these compounds also had the undesirable property of existing as a mixture of four interconverting rotational isomers. Through biological and structural analysis of the atropisomers, a binding model was developed and used to guide the design of compounds, which were rigidified by installation of a cyclizing linkage. These compounds existed as a mixture of two atropisomers. Further elaboration of the ring system reinforced the desired conformation and eliminated atropisomeric properties. We found that the region distal to the 8-membered ring system could be modified while retaining NK1 potency, and optimization led to further improvements in the in vivo activity. 相似文献